A key objective in current neurobiological research is to understand how excitable cells such as neurons are able to both generate and utilize ionic gradients across their membranes. A better understanding of the mechanisms which regulate the ionic permeability of excitable cells will be gained from a characterization of the proteins involved in synaptic transmission and ion discharge. Neuroactive toxins can play important roles both in understanding the electrophysiological effects of specific ion channels and in isolating and characterizing the proteins involved in signal transduction. We propose to clone and express the gene which encodes a potent invertebrate neurotoxin found in the venom of the predacious mite, Pyemotes tritici. Availability of sufficient quantities of this toxin for general neurobiological studies have been severly limited due to the inconvenience of rearing large quantities of mites and the difficulty in obtaining venom from such small organisms. By inserting the mite toxin gene into an insect virus-based expression vector system, we should be able to obtain a convenient and abundant source of this toxin for further studies including analysis of its mode of action and the characterization of its target protein.